Intraoperative hyponatremia during craniofacial surgery

Hyponatremia is an important cause of morbidity in some groups of hospitalized children. Our aim is to describe the incidence and severity of intraoperative hyponatremia in children undergoing craniofacial surgery, and determine the associated risk factors.

A descriptive retrospective study of children who underwent primary craniofacial surgery between March 1994 and February 2008 was performed. All administered fluids contained a minimum sodium concentration of 140 mmol.l(-1). Hyponatremia was classified as follows: severe < or =125 mmol.l(-1); moderate 126-130 mmol.l(-1); and, mild 131-134 mmol.l(-1).

Hundred and seven cases are reported. Severe, moderate and mild intraoperative hyponatremia occurred in 14 (13%), 21 (19%) and 23 (22%) children respectively. Mannitol was given to 31 (29%) children, but was not associated with the development of hyponatremia. Neither the type nor duration of surgery, type of fluid replacement nor hourly urinary output, was associated with development of hyponatremia. Most episodes of significant intraoperative hyponatremia (44%) were detected between the 2nd and the 4th hour of surgery. There were no identified neurological sequelae (e.g. coma, neurological deficit) attributable to the hyponatremia.

Despite strict avoidance of low sodium solutions (<140 mmol.l(-1)), hyponatremia occurs frequently in children undergoing craniofacial surgery in our practice; and is unrelated to the administration of mannitol. Although the mechanisms are yet to be determined, anesthesiologists should be aware of this issue and be prepared to monitor and treat this potentially serious complication.